appear to be unusually efficient vectors of a variety of disease causing organisms. In their immature stages, they often feed on birds, rodents, and hares that are important reservoirs of pathogens, especially viruses and rickettsiae. Few ticks have been incriminated as reservoirs and vectors of pathogenic viruses, but several species of hyalommas are known to be hosts and vectors of the viruses causing several distinctive acute infectious hemorrhagic fevers of human beings in the Soviet Union. Unpublished studies by Daubney (conversation) indicate that one of these same species may transmit in nature the virus causing a Near Eastern encephalomyelitis of equines. These same tick species occur in North Africa and northern Sudan. Other species cause paralysis of man and animals, apparently as a result of toxins injected into the host while the tick is feeding. The association of Hyalomma ticks with a number of other human and veterinary diseases is noted in the following text. Many Hyalomma species, in our experience, attach readily to man and feed on him. The "cursorial ticks" of North African and Arabian deserts, as first described by Mann (1915), are several species of hyalommas that come rushing from beneath every shrub when persons or animals stop nearby. These are almost invariably unfed adults, of uniform size, shape, color and general appearance, that have molted from the nymphal stage in rodent burrows beneath shrubs. Although few of these highly agitated young adults actual ly attach to man, some do. Confusion in nomenclature has limited the value of many earlier studies on biology and disease transmission in this group, for it is often impossible to be certain which species the writer used in his work. Considerable study on this genus has been and is being done in Russia, and it is frequently difficult for reviewers to determine exactly the species being reported and to satisfactorily evaluate the reports. In addition, it should be indicated that the range of Hyalomma ticks covers, in large part, a vastly undeveloped part of the world in which little serious scientific research has been accomplished. Before many years have elapsed, enough evidence probably will have been presented to indicate that Hyalomma ticks are economically among the most important of animal ectoparasites to be found anywhere in the world. IDENTIFICATION Use of the following key should never be attempted without reference to the section on identification for each species men tioned in the text. In the identification section, an attempt has been made to present lucidly all important characters of typical specimens and to indicate the range of variability seen in each species. I am most grateful to Mr. Makram N. Kaiser, Chief Technician in the Department of Medical Zoology at U.S. Naval Medical Research Unit, who has served as a "sounding board" and has given invaluable assistance in grouping the very large numbers of specimens that have been studied and often restudied for this section. Special acknowledgement should also be made of the services of Dr. L. P. Delpy, who initially iden tified many of our early collections of Hyalomma and of Mr. Glen Kohls who has spent several days conferring over specimens in the Schulze collection, now deposited in the Rocky Mountain Laboratory at Hamilton, Montana. Persons attempting to identify field collected material of Hyalomma should recognize that a certain proportion of spec_ imens in many series will defy final determination of species. These had best be called "Hyalomma species" and sent to a capable specialist in the group or put aside for further study as addi tional information becomes available. *In H. excavatum, and sometimes in other species that have en gorged on large animals such as camels, and have considerably stretched their integument, the subanal shields may be laterally displaced. Such excavatum specimens would appear to be H. dromedarii, except for smaller size, fewer and smaller scutal punctations, and differences in the caudal area of the scutum. See also identification of H. impeltatum for superficial varia tion among unfed males, which may cause them to be suggestive of H. marginatum. 3. Lateral grooves not extending beyond Lateral grooves extending beyond the 4. Scutum smooth, bright*, with very few, Scutum densely punctate, or with dense, contiguous punctations posteriorly.. 5. Scutum densely, entirely, and almost always uniformly covered by puncta tions often obscuring the lateral grooves.. Scutum irregularly punctate, or ..H. EXCAVATUM Figures 166 and 167 ..4 .H. DETRITUM Figures 158 and 159 *Do not confuse this with H. truncatum that has a smooth, shiny scutum but also dense punctations in a rectangular field poste riorly. ..5 .6 .7 |